1. Field of the Invention
The present invention relates to a method of manufacturing a magnetic head for recording/reproducing data in/from a magnetic recording medium and, more particularly, to a method of manufacturing a magnetic head in which at least parts of a pair of magnetic cores are brought into contact with an adhesive.
2. Description of the Related Art
Various types of magnetic head for use in, e.g., a video tape recorder, a floppy disk apparatus, and a hard disk apparatus have been conventionally developed. As a magnetic tape having a high coercive force and a high residual flux density corresponding to an increased density of a recording medium, a head called an MIG (Metal In Gap) head having a high saturated flux density and a low residual flux density has been developed. This MIG head is obtained by sandwiching a gap formed between magnetic cores consisting of, e.g., ferrite by metal magnetic layers consisting of, e.g., Sendust or an amorphous metal magnetic material.
In such a conventional magnetic head, opposing core main bodies are formed of a pair of magnetic cores consisting of, e.g., ferrite, and a gap formed of a non-magnetic layer consisting of, e.g., SiO.sub.2 is sandwiched by metal magnetic layers between the magnetic cores. In this magnetic head, track widths are formed at a predetermined pitch on each magnetic core, and regulation grooves are formed between the track widths. The metal magnetic layer having a thickness of, e.g., 4 to 8 .mu.m is formed on the surface opposing the track widths by sputtering, and the non-magnetic layer having a thickness of about 0.2 to 0.5 .mu.m is similarly formed on the metal magnetic layer by sputtering. The magnetic cores each having the metal magnetic layer and the non-magnetic layer are fused and bonded with each other by an adhesive such as glass so that the surfaces opposing the track widths oppose each other. The bonded magnetic cores are cut by the predetermined pitch, and a portion to serve as a tape contact surface is polished, thereby forming a magnetic head.
In the case of a magnetic head consisting of ferrite (to be referred to as a ferrite head hereinafter), if a predetermined stress remains in ferrite in a chip, the permeability of the core in a magnetic flux flowing direction is increased although the degree of increase depends on the composition of ferrite. As a result, reproducing efficiency of the magnetic head is significantly increased.
Although the MIG head has good recording performance, its reproduction efficiency is lower than that of the ferrite head. That is, a reproduction output obtained by the ferrite head is higher than that obtained by the MIG head. Therefore, in order to obtain a better MIG head, it is important to increase the permeability.
In order to increase the permeability, however, if a suitable difference is given between thermal expansion coefficients of the adhesive (glass) and the magnetic core (ferrite), the following problem is posed. That is, in the MIG head, the metal magnetic layer is formed between the adhesive and the magnetic core. For this reason, a stress caused by a difference between the thermal expansion coefficients of the adhesive and the magnetic core is not transmitted to the magnetic core. Therefore, the metal magnetic layer tends to deform, or the magnetic core and the metal magnetic layer are easily peeled at their interface. In addition, since the metal magnetic layer is present between the adhesives for bonding the opposing magnetic cores, a similar problem is posed in terms of bonding strength of the adhesive for bonding the magnetic cores.
When the magnetic core and the metal magnetic layer are peeled at their interface, a so-called pseudo gap is undesirably produced due to peeling between the magnetic core and the metal magnetic layer in a recording medium sliding portion corresponding to the track widths. Unlike frequency characteristics obtained by a normal gap, an output obtained by the pseudo gap degrades head characteristics. Therefore, it is difficult to obtain desired head characteristics.